Manufacture of grease compositions



March 11, 1952 Filed May 16, 1949] R. J. MOORE ETAL 2,588,556

MANUFACTURE OF GREASE COMPOSITIONS 2 SHEETS-SHEET 1 620.6? Y HOMOGE/V/Zff INVENTORS ROBERT J. MOORE, AND WALFRID sAA g am THEIR ATTORNEY F/GUEE March 1952 R. J. MOORE ET AL 2,588,556

MANUFACTURE OF GREASE COMPOSITIONS Filed May 16, 1949 2 SHEETSSHEET 2 F/MPE 2 C: Q Q Q Q Q m 5: a a a Q Ala/wauwdaa'a/w 0;: u saw/r ,un/ms my lNV ENTORS ROBERT J. MOORE,AND WALFRID SAARNI THEIR ATTORNEY Patented Mar. 11, 1952 MANUFACTURE OF GREASE COMPOSITIONS Robert J. Moore, Oakland, and Walfrid Saarni, Berkeley, Calif., assignors to Shell Development Company, San Francisco, Ca-lif., a corporation of Delaware Application May 16, 1949, Serial No. 93,588

13 Claims. (Cl. 252-42) 1 --This invention relates to a novel method of preparing grease compositions. More particularly, this invention pertains to a novel process of making alkali and/ or alkaline earth soap grease compositions which are stable under static or dynamic conditions, resist bleeding and possess excellent lubricating properties over wide temperature ranges.

It is well established that the quality of a grease varies substantially with the method of making it. Thus, lubricating grease compositions made from identical materials, but in which the method of making said grease has been varied, will result in one case in a grease having excellent stability and lubricating properties and in the other case the resulting grease will be extremely poor. A study of this problem makes it more and more evident that with some types of greases a controlling factor, which will determine the quality and property of the grease, is the final structure of the gel or soap used to make the grease. Unless the fibrous or micelle structure of the grease is controlled an initially good grease may become useless on working. Thus, many types of ball and roller bearing greases on being worked lose their grease-like structure and flow away from the bearing surface being lubricated and thereby leave the bearing unprotected.

The ability of controlling or modifying the fiber, crystalline or micelle structureor soaps or gelling agents used in forminggrease during the conventional grease making process isextremely difficult. One means of overcoming thisdifiiculty has been the use of crystalline or micelle modifiers. In, many cases, however, they do more harm than good, and in some cases additives which possess the ability of acting as crystalline or micelle modifiers, cause corrosion, act as prooxid'ants and the like. Bleeding is also a phenomenonfrequently encountered in greasecompositions which is manifested by an undesirable separation of soap and base lubricant. This actionhas also been termed syneresis and is thought to be due in part to the presence of an undesirable'soap' structure." Generally, to inhibit bleeding and improve the texture of greases special precautionary measures are taken, such as employing slow or rapid means of cooling, or extensively working the grease in special homogenizers, e. g. the Cornell homogenizer and the like. Such procedures are usually time-consuming and add greatly to the cost of the grease. Other ways of producing stable, nonbleeding greases have been attempted by either reducing the soap content-generally" tolessthan about 5% by weight or by increasing the soap content to a maximum. These methods of stabilizing greases against bleeding have also proved to be unsatisfactory because in the case of reducing the soap content to less than 5 such greases become limited in their use due to the low soap content, while increasing the soap content to a maximum makes the grease too costly and such products generally possess an undesired consistency.

It is an object of this invention to produce greases by a novel process. Another object of this invention is to produce greases by a novel process which is stable under static and dynamic conditions. Another object of this invention is to produce greases by a novel process which resists bleeding. Still another object of this invention is to provide a method of making greases having a definite micelle or soap struc-' ture. Still another object of this invention is to provide a method of making greases in a batch or continuous process whereby mechanically stable, non-bleeding products are produced. Still another object of this invention is to produce a grease of desired consistency with a minimum amount of soap.

Broadly, this invention comprises a method of making alkali and/or alkaline earth soap greases involving the following essential steps. A prema'de soap or saponifying agents and saponifiable materials are admixed with a portion of the base oil required to make the grease and the mixture heated to above the melting point of the soap or mixtures thereof until a homogeneous mass has been obtained. If only a portion of the base oil has been used to form the homogeneous mass, the remainder of the base oil can be added at this point together with any additives or modifying agents which might be desired to have present in the final product. The homogeneous grease mass is then cooled from above its temperature of transition to the jelly phase to below this transition temperature but above C. and the grease is heat-treated at a convenient temperature between 100 C. and the transition temperature in a quiescent state until the desired soap fiber growth has been attained. The grease can then be slowly'cooled with or Without stirring down'to room temperature or shock-chilled to room temperature, homogenized, if desired, and packaged.

The essence of this invention then is to heat-' treat alkali and/or alkaline earth soap greases while they are in the expanded gel phase until a recrystallization and consolidation of soap crystallites into the desired fiber form have been attained. The gel phase may be defined as a two phase system comprising solid crystalline soap and a liquid phase consisting of either soapoil jelly or pure oil. The jelly phase of the system under discussion may be defined as being a non-crystalline mixture of soap and oil and may be considered as a single-phase system or a pseudo-solution. Within the limits of the expanded gel phase, recrystallization and'consolidation of soap crystallites proceeds at a rate dependent upon the temperature so that a lower temperature can be compensated for by increased heating time. By plotting a cooling curve for a particular soap grease (temperature versus time) and integrating that portion above 100 C. and below the jelly phase, a term comprising the product of time (t) and temperature (T C.) can be obtained which can be correlated with the mechanical stability of the resulting grease. That is, for a given mechanical stability (t) (T-100)=K (I).

The soap used to make greases of this invention may be made by saponification of various fats, fatty acids, derivatives of fats and oils such as fatty acids derived from vegetable, animal, marine and fish oils, and hydrogenated fatty acids thereof; preferably containing from 8 to 40 carbon atoms, synthetic fatty acids produced from hydrocarbon, naphthenic acids, rosin acids, tall oil acids and the like.

Specifically, the natural fats and fatty acid materials derived therefrom which can be used toform soaps include:

I. Animal:

Tallow (beef, mutton, goat) etc., lard oil, bone oil, neats-foot oil, wool fat, horse fat oil, etc.

II. Vegetable oils:

Caster oil, cashew nut oil, peanut oil, cocoanut oil, jojoba seed oil, olive oil, palm oil, corn oil, cottonseed oil, rapeseed oil, ravison oil, sesame oil, soyabean oil, linseed oil, etc.

III. Marine and fish oils:

, Codfish oil, codliver oil, dog fish oil, dolphin oil, herring oil, menhaden oil, porpoise oil, salmon oil, sardine oil, seal oil, shark oil, whale oil, etc.

IV. Hydrogenated residuum or distillate fractions obtained from any of the oils listedabove.

V. Specific fatty acids which can be used to form the soap may include saturated alkyl monocarboxylic acids:

Capric, undecylic, lauric, myristic', palmitic, stearic, arachidic, lignoceric, montanic, melistic acids, etc.

Va. Unsaturated alkyl monocarboxylic acids:

Oleic, linoleic, erucic, clupanodonic, linolenic,, brassidic, elaidic, elacosteanic, stearoleic acids, etc.

Mixtures of fatty materials and derivatives thereof may be used to form soap. Thus, an excellent soap for grease compositions may be made from a mixture of hydrogenated fish oil fatty acids and hydrogenated caster oil. The propor above type fatty materials, their mixtures, with metal oxide, hydroxides, carbonates, etc;, or in the presence of several metal compounds, or or-- ganic bases.

A. Metals selected from the periodic table, e.g.,-- Group Ilithium, sodium, potassium, rubidlum, (388111111. 4 Group II-calcium, strontium, barium, magnesium, zinc, and cadmium.

In order more clearly to set forth the invention, reference is now made to the accompanying drawing, which is a fiow diagram illustrating a method of producing alkali and/or alkaline earth soap greases by the meaning of this invention. It is understood that modifications as to equipment, its arrangement, type and kind of materials and their proportions can be resorted to without departing from the spirit of the invention as presented in the subjoined claims.

Referring to the flow diagram, the invention cambe carried out as follows: Into a slurry tank I a pre-made soap or soap mixtures or materials used for making desired soaps and base oil are added through lines 3 and 2, respectively. If other additives such as oxidation and corrosion inhibitors, anti-bleeding agents, oiliness agents, fillers and the like are added to the grease they can be introduced into the slurry tank I through conduit 3 or through conduit 2| at a convenient time. The oil and soap are heated to between about 60 and C. and preferably to :80" C. and then led through conduit 4 to conduit H to a slurry homogenizer l where the oil-soap mixture is workedv at atemperature of about C. The mixture can then be returned to the slurry tank I throughlines42 and 43 for further working or by-passed through line 4 through pump 6' and line 4" into heating tank 8. If the mixture is returned to slurry tank I for further working it is subsequently discharged from the tank into line 4' through a booster pump 5 on through line 4" and pump 6, throughline 4 and into heating tank 8-. If only a portion or the base oil has been used the balance of the oil is added at this point through line 2|, and the entire mixture is stirred and heated at a temperature offrom l80'to 250 C. until a homogeneous mixture has been attained. During this stage of the process additives can be added to the grease if so desired. The heating vessel 8 may be aheating'kettle or a heating votator or any suitable equipment for making a desired grease composition. The-hot grease is then discharged from the vessel 8 at a controlled rate through lines 9 and 9 with the aid of pump I 0 so that when it reaches the time tank I i it is at the temperature where it is just changing its phase from a jelly'phase to a gel phase. The grease is allowedto remain in the time tank H at a temperature and for a time 2 to 10 hoursv which would allow for the maximum recrystallization and consolidation of soap crystallites into fibers of desired length and structure while in a quiescent state. Fora grease having a desired mechanical stability, the time and temperaturefactors can be determined by Formula I, column 3. The grease is discharged from the time tank II and may be conducted through lines l2 and i4 into a slow cooling tank 45 or conducted through lines I 2 and I3 into an apparatus 44 where the grease can be quickly cooled to room temperature. This can be accomplished'by use of a steel belt on which the grease is spread and in very thin layers and is subjected to a cooling medium or a chilled steel cylinder or a Carbondale chiller or the like canbe used; If desired, a portion of Sodium hydroxide (dissolved in 2 lbs. water) the grease can be cooling in 44 and a portion in and when both have been cooled down to room temperature the grease can be conducted through lines l3, l4 and I5 'into storage tank l6 or the entire grease can be slowly cooled to room temperature in 45. The grease is accumulated in storage tank It and may be conducted through line 36 to packing containers 20 or homogenized in a homogenizer 18 at a temperature ranging from room temperature to about C. and then discharged through line l9 into packing containers 20.

Modifications to the process outlined above can bemade. For example, the mixture of soap and oil from slurry tank l can be introduced directly into heating vessel 8 through lines 4, M, 38, 48 and 4". A portion of the grease from heating tank 8 can then be returned to the slurry tank l or slurry homogenizer I Where it is admixed with new grease, while the balance of the grease is ment by means of conduits, as noted in Figure 1,

each having attached thereto control valves 22.

To illustrate the process of making greases by this invention, a specific example, namely, the

method of'making and heat-treating a soda base grease, will be herein fully described following the fiow diagram.

The composition of the grease is as follows:

Components Hydrogenated fish oil acids Hydro enated castor oil Polfyeotgiylene glycol having an averag mo ular Solvent Refined Mineral oil, 600 sec at r ..i

The acids and glycerides together with about twice their weight of oil and the caustic solution are introduced into slurry tank I and heated at about 80 C. until the fatty materials have melted. The mixture is stirred vigorously to form a slurry and the temperature increased to above 100 C.- to

drive off the water. During the heating and stirring, a modicum of a polymeric silicone, e. g.,

dimethyl silicone polymer may be added if foam- .ing becomes excessive.

The slurry is then led through conduit 4, 4 and 4 with the aid of pumps 5 and 6 into-tank 8 where the temperature is increased to 180 to250 C. and the balance of the oil, preferably pre-heated to around C. is

4 ,The grease is then discharged through conduit 9 and 9'- with the aid of pump l0 at a rate that by the time it reaches the time tank I I the temperature of the grease is'below 172 C. The grease is allowedto remain in the time tank ll in a quiescent state. for about 8 hours at a temperature of from to C. If a substantially .lower temperaturev is to be used for bestcondifl'ti'oning 'thelgrease, should not be brought down to below" 160-170" C. in less than half an'hour. At

.the..end .o th s h t t eatm t t e grease is transferred'to'a cooling vessel 45 where it is allowed to cool to around room temperature and then led to homogenizer H! for working to a homogeneous consistency and texture, after which it is packed in containers 20. Greases produced by this method require less soap than greases produced by conventional methods. Generally, excellent greases can be produced by the present method using only 3 to 8% soap. However, if desired, larger amounts up to 30% soap and soap mixtures can be used.

Using the Formula I it is possible to accumulate data for particular types of greases from which a master curve can be plotted and from which the heat conditioning required to obtain a given mechanical stability can be predicted. Figure 2 is a master curve for the soda base grease described in the preceding paragraph. For this particular grease it can be noted from Figure 2 that an increase in mechanical stability (measured by the Shell Roll Test) is obtained with increase in heat conditioning up to an equivalent of 8 hours at 170 C. Beyond this degree of heat conditioning, a moderate decrease in mechanical stability is noted which may be related to some type of embrittlement of the fibers.

Other grease compositions which can be produced, by this process may include, sodium stearate, sodium oleate, potassium oleate, calcium stearate, barium stearate-acetate, strontium stearate-acetate, sodium 12-hydroxy stearateoleate, zinc stearate, magnesium stearate sodium palmitate, sodium soap of caster oil, sodium ricinoleate-stearate greases, and the like. These greases may contain anti-oxidants, e. g., phenylalpha-naphthylamine, fillers, etc.

The temperature at which the soap-oil system is converted from the gel (two phase) state to the jelly or solution state is affected by the mineral oil as well as by the specific soap used. In the case of the soda base grease described in the foregoing example, use of a higher molecular weight mineral oil substantially increases this transition temperature. If a lithium soap is used instead of sodium soap, the transition temperature is also increased.

To improve grease compositions made by the present method minor amounts of stabilizing agents can be added at a desired stage of the process.

A particularly desirable stabilizing agent which can be used with grease compositions of this invention are the alkylene glycol and/or alkylene thio glycol polymers as well as their mono-esters and ether polymeric derivatives. The alkylene glycolpolymeric materials can be represented by the following general structural formula:

"made by reacting n-butanol with propylene oxide at between about 212 to 230 F. under pressure and 'in'thepresen'c'e of an alkali catalyst.

The polymerized higher polyalkylene 'g-lycols having between 2 and 6 carbon atoms in the alkylene group are most effective as additives of this invention and those containing the ethylene and propylene groups are preferred. The average molecular weight of the polyalkylene glycols may be from about 200 to about '7000 and the preferred molecular weight being from about 600 to 6000. 7

It is desired to point out that the higher polyalkyle'ne glyccls are composed of mixtures of several polymers, for example, a polyethylene glycol having an average molecular weight of 400 consists of various glycols varying from a minor amount of monoethylene glycol and increasing up to the pentadecaethylene glycol. Therefore, it is the average molecular weight which is specified and wherein the present specification, polyalkylene glycols or polyethylene glycols are referred to, they define the higher glycols having an average molecular weight in excess of 200 and preferably in excess of 400, those with an average molecular weight of between 600 to 1500 being very effective in carrying out the present invention.

In lieu of the polyalkylene glycols, the ester and ether derivatives can be used. The esters can be made from a variety of acids having between 1 to about 22 carbon atoms and preferably between about 10 to 18 carbon atoms. Acids which may be used are the aliphatic, aromatic, cyclic, s'ulfonic acids and the like. Fatty acids and especially the higher fatty acids are preferred and include such acids as lauric, myristic. palmitic, stearic, arachidic, behenic, oleic, ricinoleic, hydroxystearic, phenylacetic', phenylstearic acids and the like. However, such acids as naphthenic acid, oil-soluble, petroleum sulfonic acids, tall oil fatty acids, aromatic acids, e. g. salicylic and phthalic acids and the like may be used to form the esters. Specific examples of esters of this type are the polyethylene glycol monostearate, polyethylene glycol monooleate and the like.

Ether derivatives of polyalkyleneglycols may be made by any conventional method and the aromatic ethers of polyalkylene glycols having the general formula:

III 2 wherein Ar is an aromatic radical having attached thereto at least one alkyl radical denoted by R having from 1 to about 8 carbon atoms and wherein Y is a fatty acid derivative, 11, m, and a are integers as in II and q is a number selected from the group consisting of zero or 1.

During the cooking of grease of this invention, there may be introduced small amounts of other soaps or salts, generally in amounts of less than 2% for additional benefits. For example, there may be incorporated into sodium soap grease as described above a minor amount of aluminum or lithium soap or alkali andalkaline earth metal naphthenates, acetates, etc.

Minor amounts of oxidation inhibitors can be added to grease compositions of this invention such as N-butyl paraphenylene diamine. Also effective as oxidation inhibitors are alpha or beta naphthalamine, phenyl-alpha or beta. naphthylamine, alpha-alpha, beta-beta dinaphthylamine, diphenylamine, tetra-methyl diamino diphenylmethane, petroleum alkyl phenols, and 2 ,4-ditertiary butyl G-methyl phenol.

Corrosion inhibitors which are particularly applicable with compositions of this invention are N-primary amines containing at least 6 and more than 18 carbon atoms in the molecule such as hexylamine, octylamine, decylamine, dodecylamine, octadecylamine, heterocyclic nitrogen containing organic compounds such as alkyl substituted oxazolines and oxazoline salts of fatty acids. I

Extreme pressure agents can be added to such grease and the preferred agents comprise esters of phosphorus acids such as triaryl, alkylhydroxy, alkyl, aralkyl phosphates, thiophosphates, or phosphites, etc., neutral aromatic sulfur compounds such as diaryl sulfides and polysulfides, e. g. diphenyl sulfide, dicresol sulfide, dibenzyl sulfide, methyl butyl diphenol sulfide, etc., diphenyl selenide and diselenide, dicresol selenide and polyselenide, etc., sulfurized fatty oils or esters of fatty acids and monohydric alcohols, e. g. sperm oil, jojoba oil, etc., in which the sulfur is tightly bound; sulfurized long-chain olefins obtained by dehydrogenation or cracking of wax; sulfurized phosphorized fatty oils, acids, esters and ketones, phosphorus acid esters having sulfurized organic radicals, such as esters of phosphoric or phosphorus acids with hydroxy fatty acids, chlorinated hydrocarbons such as chlorinated parafiins, aromatic hydrocarbons, terpenes, mineral lubricating oils, etc.; or chlorinated esters of fatty acids containing the chicrine in positions other than the alpha position.

Additional ingredients which can be added are anti-wear agents such as oil-soluble urea or thiourea derivatives, e. g., urethanes, allophanates, carbazides, carbazones, etc.; or rubber, polyisobutylene, polyvinyl esters, etc.; VI improvers such as polyisobutylene having a molecular weight above about 800, voltolizcd parafiin wax, unsaturated polymerized esters of fatty acids and monohydric alcohols, etc.; oiliness agents such as stearic and oleic acids and pour point depressor-s such as chlorinated naphthalene to further lower the pour point of the lubricant.

The amount of the above additives can be added to grease compositions of this invention in around about 0.01% to less than 10% by weight and preferably 0.1 to 5.0% by weight.

Greases of this invention are applicable for general automotive uses, and are excellent aircraft greases, industrial greases and the like.

We claim as our invention:

1. The method of making grease compositions from soaps of the group consisting of alkali metal soaps, alkaline earth metal soaps and mixtures thereof comprising forming a slurry of the soap and lubricating oil, said soap being present in an amount suilicient to form a grease, heating said slurry to a temperature of 180-250 C. until a homogeneous non-crystalline mixture has formed and thereafter cooling said grease to its gelation phase and heat-treating said grease below 172 C. but above 100 C. to produce a stable homogeneous grease.

2. The method as defined by claim 1 in which a small amount of an oxidation inhibitor is incorporated into the soap slurry.

3. The method of claim 1 in which a portion of the hot homogeneous non-crystalline oil-soap mixture is admixed with a new batch of soap slurry.

4. The method of claim 1 in which the grease after being heat-treated is slowly cooled to room temperature.

5. The method of claim 1 in which the grease 9 after being heat-treated is shock-chilled to room temperature.

6. The method of making a soda soap grease, which comprises forming a slurry of soda soap and a mineral lubricating oil, heating and slurry to a temperature of 180-250 C. until a homogeneous non-crystalline mixture has formed, cooling said grease to its gelation temperature and heat-treating said grease from below 172 C. to above 100 C. for from 2 to hours, in a quiescent state, to produce a stable homogeneous grease.

7. The method of claim 6 in which between 3 and 10% soda soap is used to form the grease.

8. The method of making a soda soap grease, which comprises forming a slurry of soda soap, polyalkylene glycol and a mineral lubricating oil, heating said slurry to a temperature of 180-250 C. until a homogeneou non-crystalline mixture has formed, cooling said grease to its gelation temperature and heat-treating said grease from below 172 C. to above 100 C. for from 2 to 10 hours in a quiescent state to produce a stable homogeneous grease.

9. The method of making a soda soap grease, which comprises forming a slurry of soda soap, 0.01 to 1% polyalkylene glycol and a mineral lubricating oil, heating said slurry to a temperature of 180-250 C. until a homogeneous noncrystalline mixture has formed, cooling said grease to its gelation temperature and heattreating said grease from below 172 C. to above 100 C. for from 2 to 10 hours in a quiescent state to produce a stable homogeneous grease.

10. The method of making an improved soda grease, which comprises (1) heating a mixture of 7 parts of hydrogenated fish oil acids, 1 part of hydrogenated castor oil, 1.12 parts of NaOH (dissolved in 2 parts of water) and a portion of solvent refined mineral oil and heating said mixture to about 100 C. until dehydrated, (2) increasing the temperature to around 180 0. adding 0.045 part of polyethylene glycol having average molecular weight of 600 and the balance of the mineral oil so that the total mineral oil amounts to 91.3 parts and heating said mixture at said temperature until mixture is homogeneous, (3) cooling the grease to- -170 C. and maintaining said grease at said temperature in aquiescent state for about 8 hours (4) and finally shock chilling said grease to room temperature and thereafter homogenizing said grease.

11. The method of making grease compositions which comprises forming a slurry of an alkali metal soap and lubricating oil, said soap being present in an amount sufficient to form a grease, heating said slurry to a temperature of -250 C. until a homogeneous non-crystalline mixture has formed and thereafter cooling said grease to its gelation phase and heat treating said grease at a temperature between 100 C. and 172 C. to produce a stable grease composition.

12. A method according to claim 11 wherein heat treating is carried out for a period from 2-10 hours.

13. The method of making grease compositions which comprise forming a slurry of an alka line earth metal soap and lubricating oil, said soap being present in an amount sufficient to form a grease, heating said slurry to a temperature of 180-250 C. until a homogeneous noncrystalline mixture has formed and thereafter cooling said grease to' its gelation phase and heat treating said grease at a temperature between 100 C. and 172 C. to produce a stable grease composition.

ROBERT J. MOORE.

WALFRID SAARNI.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,343,736 Beerbower et al. Mar. 7, 1944 2,381,314 Shields Aug. 7, 1945 2,475,589 Bondi July 12, 1949 

1. THE METHOD OF MAKING GREASE COMPOSITIONS FROM SOAPS OF THE GROUP CONSISTING OF ALKALI METAL SOAPS, ALKALINE EARTH METAL SOAPS AND MIXTURES THEREOF COMPRISING FORMING A SLURRY OF THE SOAP AND LUBRICATING OIL, SAID SOAP BEING PRESENT IN AN AMOUNT SUFFICIENT TO FORM A GREASE, HEATING SAID SLURRY TO A TEMPERATURE OF 180-250* C. UNTIL A HOMOGENEOUS NON-CRYSTALLINE MIXTURE HAS FORMED AND THEREAFTER COOLING SAID GREASE TO ITS GELATION PHASE AND HEAT-TREATING SAID GREASE BELOW 172* C. BUT ABOVE 100* C. TO PRODUCE A STABLE HOMOGENEOUS GREASE. 